The polymerization of ethylene, propylene and .alpha.-olefins by transition metal catalysts leads principally to the formation of linear polymers. However, in a recent international application published under the Patent Cooperation Treaty (PCT Application No. WO 96/23010), it has been disclosed that polymers having a moderate degree of branching can be synthesized by using palladium and nickel catalysts incorporating very bulky chelating .alpha.-diimine bidentate ligands. The PCT application discloses, for example, polyolefins having about 80 to about 150 branches per 1000 methylene groups, wherein for every 100 branches that are methyl branches, there are about 30 to about 90 ethyl branches, about 4 to about 20 propyl branches, about 15 to about 50 butyl branches, about 3 to about 15 amyl branches, and about 30 to about 140 hexyl or longer branches. The olefin polymers described in the PCT application are said to be useful as elastomers, molding resins, in adhesives, etc. Polymers containing monomer units derived other than from olefins are also disclosed in the PCT application; and polymers which contain olefin and olefinic ester monomer units, particularly copolymers of ethylene and methyl methacrylate and/or other acrylic esters, are said to be useful as viscosity modifiers for lubricating oils. The basis for the above PCT Application is believed to be an article by Johnson et al, published in the Journal of the American Chemical Society (New Pd(II)- and Ni(II)-Based Catalysts for Polymerization of Ethylene and .alpha.-Olefins, J. Am. Chem. Soc. 1995, 117, 6414-6415).
Another recent international patent application (PCT Application No. WO 97/02298) relates to the preparation of polyolefins by coordination polymerization of ethylene, styrene or norbornene using a catalyst comprising (a) a zerovalent tricoordinate or tetracoordinate nickel compound which has at least one labile ligand, (b) an acid of the formula HX, where X is a noncoordinating anion, and (c) at least one bulky ligand selected from a specified group thereof. At page 29, lines 25 et seq. of that PCT Application, it is suggested that the following materials (among others) should be absent during the polymerization process, or at least should not be present in an amount sufficient to affect the course of the polymerization: an organoaluminum compound; an aluminum halide; and any organometallic compound except for the nickel compounds. The polymers prepared in accordance with that PCT Application are moderately branched and are said to be useful as molding resins, films and elastomers.
Moderately branched ethylene polymers are also disclosed by de Souza et al in an article published in September 1997 ([.eta..sup.3 -methallyl-nickel-dad] PF.sub.6 Complex: New Catalyst Precursor For Ethylene Polymerization, Macromol. Rapid Commun., 1997,18,795-800). In that article, which was published after the provisional application on which this application is based, it is disclosed that [.sup.3 -methallyl-nickel-dad]PF.sub.6 is active as an ethylene polymerization catalyst when used in the presence of usual organoaluminum compounds such as diethylaluminum chloride, at low Al/Ni ratios and under mild reaction conditions.
While the hydrocarbon polymers prepared in accordance with the above-discussed PCT applications and de Souza article are characterized by a moderate degree of branching, there remains a need for relatively high molecular weight, hyperbranched, viscous, liquid hydrocarbon polymers and to a method for their preparation from simple and inexpensive olefins such as ethylene and propylene. A need also remains for derivatives of such hyperbranched hydrocarbon polymers, such as those prepared by grafting the liquid hyperbranched hydrocarbon polymers onto an aromatic ring in an organic compound or polymer, as well as to facile methods for preparing such derivatives.